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Cold Standby Server

Posted: 2010/09/23 07:54:48
by ak17_hk
Hi All,

I've maybe a very stupid question to ask, please kindly give me some hints on this. :-?

I have 2 web servers running in data centre, and I'm thinking whether I can have a cold standby server (only turned on if needed) ready there as well in case any of the 2 servers break down (I mean hardware failure). What I want to achieve is that once any of the running servers goes down, I can go to the data centre and immediately swap the harddisk (provided that the hardware problem is not related to the harddisk) from the dead machine to the standby one and then get it up and running quickly, so that I can take my time and repair the dead machine.

So, is this possible? If so, what are the requirements (hard or soft raid disks? same OS required? same hardware a must? system settings?) in order to make this happen? This maybe dumb but I really appreciate for any suggestions on this issue. Thank you! :-)

Regards,
Anthony.

Re: Cold Standby Server

Posted: 2010/09/27 15:24:45
by pschaff
If all systems have identical hardware and have all data on a single disk (or identical software RAID disks) then it a disk swap should "just work". Anything less than identical systems would mean more work to do to get the spare up and running. RAID is a good idea in any case for servers with high availability requirements. The "same OS?" question does not make much sense if you are swapping the system disks, but if you did want to have separate OS disks and just swap data disks, then keeping the OS the same (including updates) would be highly recommended. That would add quite a bit of complexity to the approach as both OS and application config files would have to be kept in sync.

Re: Cold Standby Server

Posted: 2010/09/28 14:28:30
by ak17_hk
Thank you for your suggestions! I'll have a go on this.

Re: Cold Standby Server

Posted: 2010/09/29 13:57:22
by pschaff
You are welcome. Please update the thread with your experiences for the sake of future forum searchers.

Re: Cold Standby Server

Posted: 2010/09/29 15:06:19
by ak17_hk
[quote]
pschaff wrote:
You are welcome. Please update the thread with your experiences for the sake of future forum searchers.[/quote]

Yup, sure!! :-)

Re: Cold Standby Server

Posted: 2010/09/30 21:55:11
by majun
I can tell from experience that it works just fine, we keep a cold standby server with no hard disks in every factory in order to have a replacement ready within minutes in case a server fails. You will have to update your network configuration on the new server though since CentOS goes by MAC address.

What you do: delete /etc/sysconfig/networking/devices/*.bak, /etc/sysconfig/networking/profiles/default/*.bak and /etc/network-scripts/*.bak, then start setup and reconfigure your network. That should be all.

Re: Cold Standby Server

Posted: 2010/09/30 23:06:44
by pschaff
... if and only if the hardware is identical and the disk contains the whole OS plus user/application data.

May not need to do [b]majun[/b]'s magic incantations, depending on how the networking was configured.

Re: Cold Standby Server

Posted: 2010/10/01 03:57:45
by ak17_hk
[quote]
majun wrote:
I can tell from experience that it works just fine, we keep a cold standby server with no hard disks in every factory in order to have a replacement ready within minutes in case a server fails. You will have to update your network configuration on the new server though since CentOS goes by MAC address.

What you do: delete /etc/sysconfig/networking/devices/*.bak, /etc/sysconfig/networking/profiles/default/*.bak and /etc/network-scripts/*.bak, then start setup and reconfigure your network. That should be all.[/quote]

Thank you very much for the valuable and constructive comments and suggestions!!! :-)